1. Field of the Invention
This invention relates generally to the field of wireless communication. In particular, this invention relates to antenna systems and methods for optimizing communication link quality with intended transceivers.
2. Description of the Related Art
As new generations of handsets, gateways, and other wireless communication devices become embedded with more applications and the need for bandwidth becomes greater, new antenna systems will be required to optimize link quality. Specifically, better control of the radiated field will be required to provide better communication link quality with intended transceivers while suppressing signals from undesired transceivers.
Moreover, as these new handsets and other wireless communication devices become smaller and embedded with increasingly more applications, new antenna designs are required to address inherent limitations of these devices and to enable new capabilities. With classical antenna structures, a certain physical volume is required to produce a resonant antenna structure at a particular frequency and with a particular bandwidth. In multi-band applications, more than one such resonant antenna structure may be required. But effective implementation of such complex antenna arrays may be prohibitive due to size constraints associated with mobile devices. Additionally, it is cost prohibitive in many applications to provide multiple power amplifiers or the feed network required to excite multiple antennas.
A substantial benefit can be realized by nulling out or reducing the antenna gain in the direction of interfering sources. A common technique is to implement an antenna array, with control of the amplitude and phase of the RF signal transmitted or received by the individual antenna elements; a weighting of the signal applied to or received by the elements can be applied that will form reduced gain, or nulls, in the direction of one or multiple interferers.
A goal of this adaptive antenna design is to increase the gain in a direction which results in an improved link budget corresponding to desired connections and reducing interference from unwanted sources when compared to an omni-directional pattern. Typically, multiple antennas are assembled into an array configuration and a feed network capable of altering the amplitude and phase of the individual antennas is connected to the antennas. An algorithm is developed to modify the composite radiation pattern of the antenna array to shape the antenna beam to increase gain in directions of desired reception or transmission and decrease antenna gain in directions of interfering sources.
The difficulty of this approach is the volume required to integrate multiple antennas in a wireless device along with the complexity of designing and implementing a feed network to distribute the RF signals to multiple antenna elements. A great benefit would be realized by the use of a single driven antenna element that could provide the ability to form nulls in directions of interfering sources.